In recent years, in some cases, a controller is connected to a home area network, and communication between a device and an external server is performed via the controller (for instance, see PTL1). Thus, it is necessary to control in-home communication by safely setting the connection between the controller and each device, and to prevent impersonation connection by an unauthorized device or information leakage by interception of the content of communication.
For instance, in an authentication system in which devices perform mutual authentication using a public key certificate (electronic certificate) issued by a certification authority, a technique is known, in which at the time of first registration, the devices generate a shared key using the public key certificate, and subsequent authentication is simplified using the shared key (for instance, see PTL2).